The risk of more devastating tsunamis than previously estimated has risen because of climate change, according to new findings published today.

Tsunamis are destructive fast-moving waves that can be triggered by earthquakes, mountain slides, or meteor impacts.

They have hit the Devon and Cornwall coast at least twice before according to historians - causing large numbers of deaths and destruction.

In the 11th century a massive wave was thought to have been caused by an asteroid falling at sea and in the 18th century an earthquake off Lisbon was responsible.

But now because of sea-levels rising the risks for coastal communities around the world are growing.

In the new study researchers warned that what was previously assumed to be the 'absolute worst case' now appears to be 'modest' for what is predicted in some locations. Previous models published in 2006 show waves up to 4.5m could hit parts of Cornwall, with lower 2m waves in the Bristol Channel and North Devon.

But now those models are out of date. The new findings show the likely increase of flooding would also move further inland than previously estimated from tsunamis following earthquakes.

It would not be the first time that a tsunami has hit the South West of England.

It was first mentioned in 1014 AD in the Anglo Saxon Chronicles. Researchers have found likely tsunami deposits at Marazion Marsh, near Penzance , and Chesil Beach, Dorset, from roughly the same time period that suggest the story is more than a legend .

An excerpt from the Anglo Saxon Chronicles dated 1014 reads: "This year, on the eve of St Michael's day, came the great sea-flood, which spread wide over this land, and ran so far up as it never did before, overwhelming many towns and an innumerable multitude of people."

Twelfth-century English historian William of Malmesbury also talks of the catastrophe, describing a "tidal wave" of "astonishing size such as the memory of man cannot parallel, so as to submerge villages many miles inland and overwhelm and drown their inhabitants."

And in 1755, the Lisbon earthquake caused a three-metre (9.8ft) tsunami that struck the coast of Cornwall with 'great loss of life and property' according to 19th-century French writer Arnold Boscowitz.

Maximum tsunami wave height after a 'Lisbon event' in metres in North Devon and the Britstol Channel predicted in 2006 (Image: Defra)

The new study, published in the journal Sciences Advances, involved scientists in Singapore, Taiwan and the United States,

Dr Robert Weiss, an Associate Professor of natural hazards at Virginia Tech in the US, said: "Our research shows that sea-level rise can significantly increase the tsunami hazard, which means that smaller tsunamis in the future can have the same adverse impacts as big tsunamis would today."

He said smaller tsunamis generated by earthquakes with smaller magnitudes occur frequently and regularly around the world.

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For the study, Dr Weiss and his colleagues created computer-simulated tsunamis at current sea level and with sea-level increases of 1.5 feet and three feet in the Chinese territory of Macau.

With a population of 613,000, Macau is a densely populated coastal region located in South China that is generally safe from current tsunami risks.

At current sea level, an earthquake would need to tip past a magnitude of 8.8 to cause widespread tsunami inundation in Macau.

But with the simulated sea-level rises, the results surprised the team.

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The sea-level rise dramatically increased the frequency of tsunami-induced flooding by 1.2 to 2.4 times for the 1.5-foot increase and from 1.5 to 4.7 times for the 3-foot increase.

Prof Lin Lin Li, a senior research fellow, said: "We found that the increased inundation frequency was contributed by earthquakes of smaller magnitudes, which posed no threat at current sea level, but could cause significant inundation at higher sea-level conditions."

Dr Adam Switzer, an associate professor at the Earth Observatory of Singapore, said: "We produced a series of tsunami inundation maps for Macau using more than 5,000 tsunami simulations generated from synthetic earthquakes prepared for the Manila Trench."

The research team estimate that sea levels in the Macau region will increase by 1.5 feet by 2060 and three feet by 2100.

Aerial view of the devastated Sumatran coastal village of Kuede Teunom, destroyed by the Boxing Day tsunami in 2006 (Image: CNN?PA)

The hazard of large tsunamis in the South China Sea region primarily comes from the Manila Trench, a megathrust system that stretches from offshore Luzon in the Philippines to southern Taiwan.

The Manila Trench megathrust has not experienced an earthquake larger than a magnitude 7.8 since the 1560s. But study co-author Dr Wang Yu, from the National Taiwan University, cautioned that the region shares characteristics that resulted in the 2004 Sumatra-Andaman earthquake, as well as the devastating 2011 earthquake in northern Japan, both causing massive loss of life.

The increased dangers from tsunamis build on already known difficulties facing coastal communities worldwide: the gradual loss of land directly near coasts and increased chances of flooding even during high tides, as sea levels increase as the Earth warms.

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Dr Weiss said: "The South China Sea is an excellent starting point for such a study because it is an ocean with rapid sea-level rise and also the location of many mega cities with significant worldwide consequences if impacted.

"The study is the first if its kind on the level of detail, and many will follow our example."

He said policymakers, town planners, emergency services, and insurance firms must work together to create or insure safer coastlines.

Dr Weiss added: "Sea-level rise needs to be taken into account for planning purposes, for example for reclamation efforts but also for designing protective measures, such as seawalls or green infrastructure.

"What we assumed to be the absolute worst case a few years ago now appears to be modest for what is predicted in some locations.

"We need to study local sea-level change more comprehensively in order to create better predictive models that help to make investments in infrastructure that are or near sustainable."

An Environment Agency spokesman said: "Climate change is one of the biggest global threats we face. Globally, intense storms are becoming more frequent and climate change is already increasing sea levels around the UK coast.

"The Environment Agency plans for climate change – we build climate change projections into the design of flood defences to make sure they are fit for the future. We also keep our data and modelling under constant review and examine it rigorously after every flooding incident to ensure our plans are climate-proof.

"We work closely with local authorities and other partners who have a responsibility for managing flood risk on planning for climate change. It is important for society as a whole to think about the impacts of a changing climate when planning for the future. Future investment of all kinds will need to be resilient to extreme weather and sea-level rise."